A heat exchanger of an air conditioning system is typically configured to facilitate heat transfer between two fluids. For example, in a typical shell and tube type heat exchanger, a plurality of heat transfer tubes are positioned inside an internal space of the shell, forming a tube side. The internal space of the shell (the shell side) may be configured to carry the first fluid, and the tube side may be configured to carry the second fluid. The heat exchanger may be configured to help heat transfer between the first fluid and the second fluid in the shell side and the tube side respectively. The heat exchanger can be a condenser. The shell side of the condenser is typically a compressed refrigerant in a vapor state and the tube side of the condenser is generally a coolant, such as water. The coolant in the tube side can cool down the compressed refrigerant in the vapor state in the shell side toward a saturation temperature of the refrigerant, causing the compressed refrigerant in the vapor state to transit into a liquid state. Some condensers can also be configured to have a subcooler to further cool the refrigerant in the liquid state to below the saturation temperature of the refrigerant, producing the subcooled refrigerant. The subcooler is typically positioned toward a lower section close to a bottom of the shell side.